Ontogeny of hepatic sn-1,2-diacylglycerol content and protein kinase C activity in the neonatal rat: lack of concordance.
Xia T. | Garner S.C. | Zeisel S.H. | Coleman R.A.
Altered activity of protein kinase C has commonly been related to activator-induced changes in cellular sn-1,2-diacylglycerol (1,2-DAG) concentration. In neonatal liver 1,2-DAG can be synthesized by the developmentally expressed monoacylglycerol acyltransferase (MGAT) activity (EC 2.3.1.22). Rat liver homogenates were examined on selected days after birth to determine whether the high MGAT activity present in neonatal rat liver was associated with high 1,2-DAG concentrations and altered protein kinase C activity and location. Although MGAT specific activity peaked between days 5 and 12, 1,2-DAG concentrations declined 63% between days 1 and 10, and the activity and membrane location of protein kinase C activity remained unchanged. Liver triacylglycerol content changed little during this time period, but the phospholipid and ceramide content of liver increased about 60 and 100%, respectively. Thus, changes in cell membrane 1,2-DAG content may not always be associated with changes in protein kinase C activity because multiple factors (including 1,2-DAG, fatty acids, and sphingosine) modulate the activity of this enzyme. Glycerolipid synthesis is likely to be the primary fate of the 1,2-DAG synthesized by the monoacylglycerol pathway.
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